“I’ll tell you a good example,” the rabbi said. “A lady called me up, she said her son wants to go to the Museum of Science and Industry. They had a Harry Potter exhibit, OK? Imagine a kid, I don’t know how old he was, who was into Harry Potter needing to go to this Harry Potter exhibit. So I talked to her, I looked into it a little bit about how the exhibit was set up and it wasn’t possible. I wasn’t able to find a solution really.”

The woman on the phone with Rabbi Mordechai Millunchick was a kohain, as was her son. Kohanim, the plural form of the word, are in certain Jewish traditions a priestly clan direct descended from Moses’ brother Aaron. They are the only ones allowed to perform certain rituals at the Temple in Jerusalem. As such, they have to keep themselves ritually clean, free of impurities such as the “tumah” coming from dead bodies.

Which is why the MSI’s collection of historic body slices meant a little Jewish boy couldn’t go see Harry Potter.

It was 2009, and although the touring “Harry Potter: The Exhibition” came and went before the ongoing “YOU! The Experience!” opened that year with Body Worlds-created plasticized corpse-bits, the preserved cross-sections of an actual human body have startled the curious and MSI-goers who stumbled into the wrong stairwell for years.

“I told her, ‘Listen, lady. Wait. Tell your son to wait and maybe the exhibit will go to a different city, it’s just what happens.’ It may not be a good solution, but I told her, I said ‘Listen, your son is a kohain. I’m not. There are places today that I can go to and he is not allowed to go to, OK?’”

Contact with a dead body doesn’t mean touching. It can mean being in the same building as a dead body, or walking under the shade of a tree that overlaps a tree that overlaps a tree that casts shade on a cemetery. Kohanim can only go to the funerals of parents, spouses or their own children. Millunchick said observant kohainim interested in medicine often go into dentistry so they can avoid med school cadaver work.

“‘I’m allowed to go to a cemetery,’” Millunchick told the Harry Potter mom. “‘I’m allowed to go to a funeral home for just a friend, I can go to a museum, OK? In the times of the Messiah when the Temple’s going to be rebuilt, there’s going to be places that he’s going to be able to go to that I won’t be able to go to.’”

The only ceremony that cleanses a kohain who came in contact with death involves a red heifer meeting certain rigorous genetic standards set in Mishna. In all of history, the Mishna says, only nine heifers ever fit the bill. Observant Jews have been looking for the 10th red heifer since Romans destroyed the Temple in Jerusalem in 70 CE. The Jerusalem-based non-profit The Temple Institute has only reviewed two candidate cattle since it was founded in 1987. Both were disqualified, the most recent one in 2002.

As there’s no way to clean death impurities without the cow, avoidance has become vital. The sin is not in finding yourself in a building with a corpse, but in not immediately leaving if you discover yourself in one. Even if it has a really cool Harry Potter exhibit in it.

“‘He’s going to be able to serve God, basically. He’s going to be able to serve in the temple in a way anyone who’s not a kohain is going to be able to do, right?’ She understood that and she passed that on to her son who…”